1. Field of the Invention
The present invention relates to a technique of charging a battery pack. Particularly, the invention relates to a technique of charging various types of battery packs with a single charger.
2. Description of the Related Art
Many electric appliances such as a portable electric power tool powered by a detachable battery pack are used. Rechargeable battery cells, which can be charged repeatedly by a charger, are installed in the battery pack used in this type of electric appliances.
Battery packs are designed in various shapes in accordance with electric appliances in which they are used, and therefore an exclusive charger is provided respectively for each type of battery packs. Accordingly, in a case which users use various types of electric appliances, the users must selectively use various types of chargers in accordance with the types of battery packs.
With regard to the above-described problem, Japanese Patent Application Publication No. 2004-289897 describes a technique for charging various types of battery packs with a single charger. In this technique, an adapter arranged between a battery pack and a charger is utilized for the purpose of connecting battery packs having different shapes to a single charger.